The present invention relates to computer-aided simulation of complete radar system for evaluating the instantaneous power information as well as relevant frequency information thereof.
Simulation methods generally employ certain models according to which certain aspects in the "real world" are reproduced, i.e., simulated, and tested in accordance with the simulation model. Specifically, in the case of radar systems, simulation involves testing how a radar pulse is modified during propagation and dispersion; during refraction at a target; upon being received in the antenna; and pursuant to further processing in the receiver equipment. The result of said simulation is then used for optimizing signal processing.
The method of simulation is particularly suited in case of radar systems which link special, significant changes in amplitude and/or certain details in the frequency information with a particular characteristic, or a set of characteristics, of the target. This is, for example, employed in case of radar altitude meters, for example, for a satellite or a satellite supported piece of equipment. Another field of interest is measuring the wind speed through ascertaining a section of the back scatter of ocean waves. This being very special tasks, it is to be noted, however, that a simulation method of a general nature should be in principle usable for all different kinds of radar systems, in which, for example, some form of power measurement is conducted.
Let dp(t) be the power reflected by an aerial element dA being spaced at a distance R from the source of radar pulses. Then in accordance with the known radar equation, and for the case of a monostatic instance, this power at the output of the receiving antenna is given. ##EQU1##
Wherein ps(t-2R/c.sub.o) equals the transmission power attenuated in accordance with a two-fold transit time R/c.sub.o between a transmitter-receiver on one hand, and a target on the other hand.
G is the antenna gain; the average wavelength of the radar signal; c.sub.o is the speed of light, and is the power of reflectivity of the target.
The total power available at the receiver input is the integral over all reflected power increments of the target area. The known radar equation thus links the input power of a radar receiver with the transmission of the radar device under utilization of the propagation path and the target. The relationship is of course understood to be in dependence upon time. A concurrent explication of the frequency information contained in the signals, particularly here the instantaneous Doppler frequency shift, and, for example, frequency modulated transmittal signals, is generally impossible.
This desired information can be acquired, however, if amplitude and phase information are processed simultaneously. Methods along that line are quite expensive and work quite slowly. Moreover, in order to make such a method work, it is necessary in addition to generate statistically relevant sets of data under utilization of random programs, for example, the so-called Monte Carlo method. These methods are very time consuming, and require extensive computer capacity and computer speeds.